Two Bash scripts that can be used as timers when preparing for a presentation.
Both of them play a sound after 5, 6, and 7 minutes respectively, letting you know that you're towards the end of the planned timeframe of the presentation you're rehearsing.
In addition to the sound effect, one of them uses notify-send for desktop notifications (which include icons of flags with different colours) while the other one only prints messages of different colours to the standard terminal output.
Since I didn't come up with these ideas on my own, I see fit to mention the following sources I learned and gained inspiration from: